The trip underscores Annan's belief that Tehran is one of the key players in finding a solution to the conflict in Syria.

Annan described his talks in Damascus as 'constructive,' saying the sides agreed to move ahead with implementing a peace plan proposed by the envoy.

"We agreed to an approach which I will share with the opposition," he told reporters.

In Damascus, Annan met with embattled Syrian president Bashar Assad as well as Assad's foreign minister Walid Muallem.

Damascus reiterated their commitment to Annan`s peace plan, which has seen fighting spiral out of control since its initial ceasefire deadline passed in mid-April.

The 300 strong unarmed United Nations observer force deployed to oversee the implementation of Annan's plan has been suspended indefinitely due to the choas and violence rocking the country.

"In both meetings we reassured Annan of Syria's commitment to implement the six-point plan and hope the other side is mutually committed," Foreign Ministry spokesman Jihad Makdissi wrote on Twitter.

Meanwhile, Annan has arrived in Iran, Syria's main ally in the region in the hopes Tehran can exert pressure on Assad to honor the ceasefire.

On Saturday Annan had said that Iran should be involved in the resolution of the crisis, because it is an “actor” in the situation whose participation is necessary.

Speaking to Le Monde, the envoy stressed the role of Moscow and Teheran in dealing with the conflict in Syria, saying that there is "no alternative" to Russia’s participation in a diplomatic solution and that Iran also “cannot be ignored.”

However, Britain, France, and the United States have expressed opposition to Iran's involvement due to its controversial nuclear program – which Western leaders say is seeking nuclear weapons.

"The United States is against me, the West is against me, many regional powers and countries and the people are against me," Assad said, adding the United States "is a part of the conflict.

“They offer the umbrella and political support to those gangs to create instability (destabilize) or to destabilize Syria,” Assad told ARD.

Assad has accused the US, its Western allies, and several Gulf Arab states of supporting "terrorist forces" he claims are trying to overthrow his regime on numerous occassions during the 16-month popular uprising against his regime.

Syria has been rocked with a popular uprising now turned civil war that has left some 16,500 dead since it erupted amid the Arab Spring last March.

Assad's bloody crackdown on dissent has led to mass army defections and the emergence of the rebel Free Syrian Army, which has taken its fight into the outskirts of his stronghold, the capital city of Damascus.

The FSA, consisting of some 30,000 army defectors commanded by dissident Syrian officers who have taken refuge in neighboring Turkey, has mounted an increasingly deadly guerilla campaign of hit-and-run raids and ambushes on Assad's troops and security apparatus.

At the same time, FSA fighters have taken pains to avoid civilian casualties so as not to alienate the Syrian people - or Western and Gulf Arab nations who are believed to be supporting them.

Assad has been shielded from direct international pressure or intervention, however, by China and Russia – who have wielded their vetoes in the UN Security Council to shield Damascus.

“I do not believe that Russia and China are paying any price at all – nothing at all – for standing up on behalf of the Assad regime," US secretary of state Hillary Clinton said. "The only way that will change is if every nation represented here directly and urgently makes it clear that Russia and China will pay a price."